A large forest accipiter. Even dark grey-brown above, with slight pale supercilium and pale, heavily-barred underparts, long yellow legs and long tail. Young birds are paler brown above, often with paler feather-bases showing, and are streaked brownish underneath. Similar spp. Very similar to Madagascar Serpent Eagle Eutriorchis astur, though the adult lacks that species' overall brownish coloration and dark bars in tertials, mantle and crown-feathers. Young birds are easily distinguished by having streaks, not bars, on the underparts. Flight is generally more direct and rapid than Madagascar Serpent Eagle. Almost identical in plumage to Madagascar Sparrowhawk Accipiter madagascariensis, but much larger; differs in having throat barred and streaked, forming a chequered pattern, and in usually having bars on the undertail-coverts. Hints Often seen flying over the forest canopy calling, a loud, rapid, rather cracked "ang-ang-ang-ang-ang-ang...". Otherwise, sometimes seen briefly while chasing birds in the sub-canopy or in clearings.

Justification:
This species may have a very small population, which is threatened by deforestation and human disturbance. It is therefore listed as Near Threatened. More accurate population measures and a better understanding of a possible population decline may lead to it being raised to a higher threat category.

Accipiter henstii is a forest raptor sparsely distributed throughout most of Madagascar but absent from the south-west (Langrand 1990). It is rare throughout its range (Langrand 1990; Morris and Hawkins 1998), but appears to be present in almost all adequately large forest blocks that have been surveyed (ZICOMA 1999).

It occurs in primary forest, both dry deciduous and humid evergreen, and in some secondary woodlands and large Eucalyptus plantations, not always near primary forest, up to 1,800 m (del Hoyo et al. 1994). It has a large home range size and lives at low densities, making it vulnerable to population declines, and may be declining more rapidly than currently thought (R. Thorstrom in litt. 2016). It hunts below the canopy for birds and small mammals, probably including some lemurs (Langrand 1990; Morris and Hawkins 1998). Egg-laying takes place in October-November, and the nest is large and constructed from sticks in the main fork of large trees, including those in Eucalyptus plantations (del Hoyo et al. 1994).

Conservation Actions ProposedConduct surveys to establish an up-to-date estimate of its population and range. Study the species's ecology, in particular in rainforest and dry forest habitats (R. Thorstrom in litt. 2016). Monitor rates of deforestation across its range. Secure habitat through protected area status.